Ca doped multi-component rare-earth zintl phases Yb_0.85−xCa_xCe_0.15Ag_0.85Sb and their thermoelectric performance modulation

Multi-component Zintl phase compounds, combining structural complexity with tunable electrical and thermal transport properties, are promising thermoelectric materials. In this work, rare-earth Zintl phase antimonides Yb_0.85RE_0.15Ag_0.85Sb (RE = La, Ce, Pr, Nd) were successfully synthesized via the Pb flux method. Single-crystal X-ray diffraction analysis revealed that all compounds in this series adopt the LiGaGe-type structure. Yb_0.85Ce_0.15Ag_0.85Sb exhibited a ZT value of approximately 0.4 at 1023 K, along with excellent high-temperature stability. To further enhance the Seebeck coefficient and reduce thermal conductivity, a series of multi-component rare-earth Zintl phase Yb_0.85−xCa_xCe_0.15Ag_0.85Sb (x = 0.1~0.6) was constructed via Ca doped multi-component solid-solution design. Benefiting from the inherently low thermal conductivity of Zintl phase compounds, the thermoelectric performance of all doped samples was significantly enhanced, showing approximately a twofold improvement compared to the undoped sample in the medium-to-high temperature region. Notably, the peak ZT temperature of Yb_0.55Ca_0.3Ce_0.15Ag_0.85Sb shifted to lower temperatures by approximately 150 K, reaching about 0.81 at 873 K. Based on DFT simulations, the doping-induced performance enhancement is attributed to the local lattice strain introduced by cation substitution and the modulation of charge distribution in the AgSb layers, which affect the density of states at the valence band maximum, thereby enabling the tuning of the hole effective mass. This work demonstrates a synergistic strategy combining multi-component solid-solution design and elemental doping to achieve effective decoupling and optimization of electrical and thermal transport, offering new insights for the design of high-performance Zintl-phase thermoelectric materials.